DTV receiver and method of processing broadcast signal in DTV receiver

ABSTRACT

A DTV receiver includes a tuner tuning to a channel to receive a broadcast signal, and a demodulator demodulating the broadcast signal. The receiver further includes a first decoder which decodes main and enhanced data included in the demodulated signal by calculating soft decision values for the enhanced data and hard decision values for the main data. The receiver further includes a second decoder for decoding the main and enhanced data for first forward error correction, and a third decoder for decoding the FEC-decoded enhanced data for second forward error correction.

This application is a continuation of U.S. Application Ser. No.12/970,841, filed on Dec. 16, 2010, now U.S. Pat. No. 7,995,669, whichis a continuation of U.S. application Ser. No. 12/852,420, filed on Aug.6, 2010, now U.S. Pat. No. 7,885,347, which is a continuation of U.S.application Ser. No. 11/615,496, filed on Dec. 22, 2006, now U.S. Pat.No. 7,796,712, which claims the benefit of Korean Patent Application No.10-2005-0128961, filed on Dec. 23, 2005, and the benefit of U.S.Provisional Application No. 60/825,269, filed on Sep. 11, 2006, whichare all hereby incorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital telecommunications system,and more particularly, to a DTV receiver and a method of processing abroadcast signal in a DTV receiver.

2. Discussion of the Related Art

The Vestigial Side Band (VSB) transmission mode, which is adopted as thestandard for digital broadcasting in North America and the Republic ofKorea, is a system that has been developed for the transmission of MPEGvideo/audio data. However, presently, the technology for processingdigital signals is being developed at a vast rate, and, as a largernumber of the population uses the Internet, digital electric appliances,computers, and the Internet are being integrated. Therefore, in order tomeet with the various requirements of the users, a system that cantransmit diverse supplemental information in addition to video/audiodata through a digital television channel needs to be developed.

Some users may assume that supplemental data broadcasting would beapplied by using a PC card or a portable device having a simple in-doorantenna attached thereto. However, when used indoors, the intensity ofthe signals may decrease due to a blockage caused by the walls ordisturbance caused by approaching or proximate mobile objects.Accordingly, the quality of the received digital signals may bedeteriorated due to a ghost effect and noise caused by reflected waves.However, unlike the general video/audio data, when transmitting thesupplemental data, the data that is to be transmitted should have a lowerror ratio. More specifically, in case of the video/audio data, errorsthat are not perceived or acknowledged through the eyes or ears of theuser can be ignored, since they do not cause any or much trouble.Conversely, in case of the supplemental data (e.g., program executionfile, stock information, etc.), an error even in a single bit may causea serious problem. Therefore, a system highly resistant to ghost effectsand noise is required to be developed.

The supplemental data are generally transmitted by a time-divisionmethod through the same channel as the MPEG video/audio data. However,with the advent of digital broadcasting, ATSC VSB digital televisionreceivers that receive only MPEG video/audio data are already suppliedto the market. Therefore, the supplemental data that are transmittedthrough the same channel as the MPEG video/audio data should notinfluence the conventional ATSC VSB receivers that are provided in themarket. In other words, this may be defined as ATSC VSB compatibility,and the supplemental data broadcast system should be compatible with theATSC VSB system. Herein, the supplemental data may also be referred toas enhanced data. Furthermore, in a poor channel environment, thereceiving performance of the conventional ATSC VSB receiving system maybe deteriorated. More specifically, resistance to changes in channelsand noise is more highly required when using portable and/or mobilereceivers.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a DTV receiver and amethod of processing a broadcast signal in a DTV receiver thatsubstantially obviates one or more problems due to limitations anddisadvantages of the related art.

An object of the present invention is to provide to a DTV receiver and amethod of processing a broadcast signal in a DTV receiver that canperform a soft decision on a set of received enhanced data so as toperform additional error correction decoding.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, adigital television (DTV) receiver includes a tuner, a demodulator, asoft-in-soft-out (SISO) decoder, a first forward-error-correction (FEC)decoder, and a second FEC decoder. The tuner initially tunes to achannel to receive a broadcast signal. The demodulator then demodulatesthe broadcast signal. The SISO decoder decodes main and enhanced dataincluded in the demodulated signal by calculating soft decision valuesfor the enhanced data and hard decision values for the main data. Forexample, the soft decision values may be obtained by calculatinglog-likelihood-ratio (LLR) values for the enhanced data. The first FECdecoder decodes the SISO-decoded main and enhanced data for first FEC,and the second FEC decoder decodes the FEC-decoded enhanced data forsecond FEC.

The DTV receiver according to the present invention further includes aderandomizer which derandomizes the main and enhanced data decoded bythe first FEC decoder. It bypasses or inverts each soft decision valuebased on a value of a corresponding pseudo random bit. For example,bypasses a soft decision value if a value of a corresponding random bitis 0, and it inverts the soft decision value if the random bit valueis 1. The derandomizer performs an exclusive OR (XOR) operation on thehard decision values for the main data with their corresponding pseudorandom bits, respectively. On the other hand, it obtains hard decisionvalues of the soft decision values for the enhanced data and performs anexclusive OR (XOR) operation on the hard decision values and theircorresponding pseudo random bits, respectively.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a block diagram of a digital broadcast transmittingsystem according to an embodiment of the present invention;

FIG. 2 illustrates a block diagram of a digital broadcast transmittingsystem according to another embodiment of the present invention;

FIG. 3 illustrates a block diagram showing a general structure of ademodulating unit within a receiving system according to an embodimentof the present invention;

FIG. 4 illustrates a block diagram showing the structure of a digitalbroadcast (or DTV) receiver according to an embodiment of the presentinvention; and

FIG. 5 illustrates a block diagram showing the structure of a digitalbroadcast (or DTV) receiver according to another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In addition, although the terms used in the present invention areselected from generally known and used terms, some of the termsmentioned in the description of the present invention have been selectedby the applicant at his or her discretion, the detailed meanings ofwhich are described in relevant parts of the description herein.Furthermore, it is required that the present invention is understood,not simply by the actual terms used but by the meaning of each termlying within.

In the present invention, the enhanced data may either consist of dataincluding information such as program execution files, stockinformation, weather information, and so on, or consist of video/audiodata. Additionally, the known data refer to data already known basedupon a pre-determined agreement between the transmitter and thereceiver. Furthermore, the main data consist of data that can bereceived from the conventional receiving system, wherein the main datainclude video/audio data. The present invention relates to outputting asoft decision value corresponding to a set of received enhanced data,thereby enhancing the performance of additional error correctiondecoding on the enhanced data.

FIG. 1 and FIG. 2 illustrate block diagrams of a digital television (orbroadcast) transmitting system for transmitting enhanced data accordingto preferred embodiments of the present invention. FIG. 1 and FIG. 2illustrate examples of a digital broadcast transmitting system formultiplexing and transmitting enhanced data and known data. In thepresent invention, any type of digital broadcast transmitting system fortransmitting enhanced data may be applied herein, and therefore, thedigital broadcast transmitting system is not limited to the examples setforth in the description of the present invention.

FIG. 1 illustrates a digital broadcast transmitting system according toan embodiment of the present invention. The digital broadcasttransmitting system includes an E-VSB pre-processor 101, an E-VSB packetformatter 102, a packet multiplexer 103, a data randomizer 104, ascheduler 105, an E-VSB post-processor 110, a Reed-Solomon (RS) encoder121, a data interleaves 122, a trellis encoder 123, a backwardcompatibility processor 124, a frame multiplexer 125, and a transmitter130.

In the digital broadcast transmitting system having the structure shownin FIG. 1, main data are outputted to the packet multiplexer 103 intransport packet units, and enhanced data are outputted to the E-VSBpre-processor 101. The E-VSB pre-processor 101 pre-processes theenhanced data, such as encoding additional error correction,interleaving, and inserting null data, and then outputs thepre-processed enhanced data to the E-VSB packet formatter 102.

Based upon the control of the scheduler 105, the E-VSB packet formatter102 multiplexes the pre-processed enhanced data and pre-defined knowndata (or a known data place holder), thereby configuring a group. Thedata within the group are then divided into 184-byte unit enhanced datapackets, and a 4-byte MPEG header is added to the beginning of theenhanced data packet, thereby outputting a 188-byte enhanced data packet(i.e., a MPEG compatibility packet). More specifically, one enhanceddata packet group includes a plurality of consecutive enhanced datapackets.

The output of the E-VSE packet formatter 102 is inputted to the packetmultiplexer 103. The packet multiplexer 103 time-division multiplexesthe main data packet and the enhanced data packet group in transportstream (TS) packet units and outputs the multiplexed TS packet inaccordance with the control of the scheduler 105. More specifically, thescheduler 105 generates and outputs a control signal so that the packetformatter 102 can multiplex the main data packet and the enhanced datapacket group. Accordingly, the packet multiplexer 103 receives thecontrol signal, thereby multiplexing and outputting the main data packetand the enhanced data packet group to TS packet units. As an example ofthe present invention, the process of the known data and enhanced databeing multiplexed in the E-VSB packet formatter 102 is described herein.

Meanwhile, the output of the packet multiplexer 103 is randomized by thedata randomizer and then provided to the E-VSB post-processor 110. TheE-VSB post-processor 110 includes a RS encoder 111, a data interleaver112, an E-VSB convolutional encoder 113, a data deinterleaver 114, and aRS byte remover 115. Herein, the RS encoder 111 RS-codes the output ofthe data randomizer 104 so as to add 20-byte parity data thereto.Thereafter, the processed data pass though the data interleaver 112 andare then provided to the E-VSB convolutional encoder 113.

The E-VSB convolutional encoder 113 converts the data bytes inputtedthereto to symbols, so as perform convolution-coding on only theenhanced data symbols. Thereafter, the E-VSB convolutional encoder 113converts the symbols back to bytes, which are then outputted. Morespecifically, when the output of the data interleaver 112 corresponds tothe main data or to the known data inserted in the enhanced data packet,the E-VSB convolutional encoder 113 outputs the data without anymodification. Furthermore, the E-VSB convolutional encoder 113 alsooutputs the MPEG header byte added by the E-VSB packet formatter 102 orthe RS parity byte added to the enhanced data packet by the RS encoder111 without any data modification. The output of the E-VSB convolutionalencoder 113 is deinterleaved by the data deinterleaver 114 and is thenoutputted to the RS byte remover 115 so as to have 20 bytes of paritydata removed therefrom. This process is necessary for recalculating theparity since the initial data have been modified (or changed) by theE-VSB convolutional encoder 113. The output of the RS byte remover 115is provided to the RS encoder 121.

The RS encoder 121 performs an RS-coding process identical to that ofthe conventional ATSC VSB system on the input data, thereby adding 20bytes of parity bytes at the end of the 187-byte data. Thereafter, theprocessed data re outputted to the data interleaver 122 and the backwardcompatibility processor 124. The data interleaver 122 performed aninterleaving process of the input data. Herein, the same interleavingrules as those of the data interleaver 112 are applied. The output ofthe data interleaver 122 is inputted to the trellis encoder 123.Thereafter, the trellis encoder 123 codes the inputted 2 bits to 3 bits,which are then outputted. The output of the trellis encoder 123 isinputted to the frame multiplexer 125. Then, the frame multiplexer 125inserts a field synchronization signal and a segment synchronizationsignal in the output of the trellis encoder 123, and the processed dataare outputted to the transmitter 130. The transmitter 130 includes apilot inserter 131, a VSB modulator 132, and a radio frequency (RF)converter 133. Since the role and operation of the transmitter 130 areidentical to those of the transmitter in the conventional VSBtransmitting system, a detailed description of the same will be omittedfor simplicity.

Meanwhile, in order to determine the output data of the trellis encoder123 as the enhanced data defined by the transmitting and receivingsystems, the memory within the trellis encoder 123 corresponding to theknown data inserted in the enhanced data packet is first required to beinitialized. In order to perform such initialization, the input of thetrellis encoder 123 needs to be replaced. Therefore, the RS parity isrecalculated in accordance with the replacement data so as to replacethe initial (or original) parity data. This process is performed by thebackward compatibility processor 124.

FIG. 2 illustrates a digital broadcast transmitting system according toanother embodiment of the present invention. The digital broadcasttransmitting system includes an E-VSB pre-processor 201, an E-VSB packetformatter 202, a packet multiplexer 203, a data randomizer 204, ascheduler 205, a Reed-Solomon encoder/parity place holder inserter 206,data interleaver 207, a byte-symbol converter 208, an E-VSB symbolprocessor 209, a known data generator 210, a symbol-byte converter 211,a non-systematic RS encoder 212, a trellis encoder 213, a framemultiplexer 214, and transmitter 220. As shown in FIG. 2, in the digitalbroadcast transmitting system having the above-described structure, amain data packet is outputted to the packet multiplexer 203, andenhanced data are outputted to the E-VSB pre-processor 201. The E-VSBpre-processor 201 pre-processes the enhanced data, such as encodingadditional error correction, interleaving, and inserting null data, andthen outputs the pre-processed enhanced data to the E-VSB packetformatter 202.

Based upon the control of the scheduler 205, the E-VSB packet formatter202 multiplexes the pre-processed enhanced data and the known data placeholder having the null data inserted therein, thereby configuring agroup. The data within the group are then divided into 184-byte unitenhanced data packets, and a 4-byte MPEG header is added to thebeginning of the enhanced data packet, thereby outputting a 188-byteenhanced data packet (i.e., a MPEG compatibility packet).

The output of the E-VSB packet formatter 202 is inputted to the packetmultiplexer 203. The packet multiplexer 203 time-division multiplexesthe main data packet and the enhanced data packet group in transportstream (TS) packet units and outputs the multiplexed TS packet inaccordance with the control of the scheduler 205. More specifically, thescheduler 205 generates and outputs a control signal so that the packetformatter 202 can multiplex the main data packet and the enhanced datapacket group. Accordingly, the packet multiplexer 203 receives thecontrol signal, thereby multiplexing and outputting the main data packetand the enhanced data packet group to TS packet units.

The output data of the packet multiplexer 203 are inputted to the datarandomizer 204. The data randomizer 204 discards (or deletes) the MPEGsynchronization byte and randomizes the remaining 187 bytes by using apseudo-random byte, which is generated from inside the data randomizer204. Thereafter, the randomized data are outputted to the Reed-Solomon(RS) encoder/parity place holder inserter 206. When the randomized datacorrespond to the main data packet, the RS encoder/parity place holderinserter 206 RS-codes the randomized data. Alternatively, when therandomized data correspond to the enhanced data packet, the RSencoder/parity place holder inserter 206 performs non-systematic RSparity place holder insertion.

The output data of the RS encoder/parity place holder inserter 206 areoutputted to the data interleaver 207. Then, the data interleaver 207interleaves and outputs the received data. At this point, the datainterleaver 207 receives a RS parity byte that is newly calculated andoutputted by the non-systematic RS encoder 212 and, then, outputs thenewly received RS parity byte instead of the non-systematic RS parityplace holder, which is not yet outputted. Each byte outputted from thedata interleaver 207 is converted into 4 symbols by the byte-symbolconverter 208, which are then inputted to the E-VSB symbol processor209. Herein, one symbol consists of 2 bits. Additionally, the known datagenerated (or created) from the known data generator 210 are alsoinputted to the E-VSB symbol processor 209. Herein, the known dataconsist of the known data symbol generated from the symbol domain. Thisis because the known data are used in the symbol domain of the receiver.Also, in the transmitter, it is more efficient to create a known datasymbol sequence having the characteristics desired (or required) by thesymbol domain.

Meanwhile, when the input data inputted to the E-VSB symbol processor209 correspond to the known data place holder that is converted to asymbol by the byte-symbol converter 208, the E-VSB symbol processor 209uses the known data generated from the known data generator 210 insteadof the known data place holder. The E-VSB symbol processor 209 thengenerates a data symbol at the beginning of the known data sequence sothat the memory of the trellis encoder 213 is initialized to apre-decided state. In order to do so, the memory value within thetrellis encoder 213 should be inputted to the E-VSB symbol processor209.

Further, the memory value of the trellis encoder 213 may also be used inan additional signaling process for the enhanced data symbol.Additionally, the trellis encoder 213 is initialized at the beginning ofthe known data sequence because a plurality of output sequences may begenerated depending upon the memory state of the trellis encoder 213even when the known data sequence is inputted to the trellis encoder213. Accordingly, the memory state of the trellis encoder 213 is firstinitialized to a pre-decided value and, then, when the known data areinputted, a desired known data output sequence may be obtained from theoutput of the trellis encoder 213. The output symbol of the E-VSB symbolprocessor 209 is inputted to the trellis encoder 213 so as to betrellis-encoded and outputted to the frame multiplexer 214.

Meanwhile, the E-VSB symbol processor 209 receives the 2-bit symbol,processes the received symbol with a plurality of process steps, andoutputs the processed symbol. Therefore, the symbol should be convertedback to bytes from the symbol-byte converter 211 so that thenon-systematic RS encoder 212 can recalculate the RS parity from theoutput of the E-VSB symbol processor 209. In other words, the inputsymbol is converted to byte units from the symbol-byte converter 211 andoutputted to the non-systematic RS encoder 212. The non-systematic RSencoder 212 calculates the 20-byte RS parity for the data packetconfigured of 187 information bytes and outputs the calculated RS parityto the data interleaver 207. The data interleaver 207 receives the RSparity byte calculated and outputted from the non-systematic RS encoder212 and replaces the non-systematic place holder that is not yetoutputted with the received RS parity byte.

Herein, since the enhanced data symbol and the known data place holderare changed to different values by the E-VSB symbol processor 209, adecoding error occurs when performing a RS decoding process in theconventional ATSC VSB receiver. The non-systematic RS coding process isperformed in order to prevent such decoding error from occurring. Theframe multiplexer 214 inserts 4 segment synchronization symbols in eachof the 828 output symbols of the trellis encoder 213, therebyconfiguring a data segment having 832 data symbols. More specifically,one field synchronization segment is inserted in each of the 312 datasegments, so as to configure one data field, which is then outputted tothe transmitter 220. The transmitter 220 inserts a pilot signal in theoutput of the frame multiplexer 214, the output having a segmentsynchronization signal and a field synchronization signal insertedtherein. The transmitter 220 then VSB modulates the pilot signalinserted data and converts the VSB modulated data to an RF signal, whichis transmitted through the antenna. Accordingly, the transmitter 220includes a pilot inserter 221, a VSB modulator 222, and a RF-UPconverter 223. Furthermore, a pre-equalizer filter may be optionallyincluded.

FIG. 3 illustrates a block diagram showing the structure of ademodulating unit within a digital broadcast receiving system thatreceives and processes enhanced data and known data that are multiplexedand transmitted. The demodulating unit may be applied to digitalbroadcast transmitting system shown in both FIG. 1 and FIG. 2.Furthermore, since any type of demodulating unit that can demodulateenhanced data may be applied to the present invention, the presentinvention is not limited to the examples set forth herein. In otherwords, the demodulating unit shown in FIG. 3 is merely an exampleintroduced for a better understanding of the present invention.

The demodulating unit uses the known data information inserted in anenhanced data section and transmitted by the transmitting system, so asto restore the carrier wave synchronization, restore the framesynchronization, and perform channel equalization, thereby enhancing thereceiving performance of the present invention.

Referring to FIG. 3, the demodulating unit includes a demodulator 301,an equalizer 302, a known data (or sequence) detector 303, asoft-in-soft-out (SISO) decoder 304, a data deinterleaver 305, a RSdecoder/non-systematic RS parity remover 306, and a derandomizer 307.The digital broadcast receiving system further includes a main datapacket remover 308, an E-VSB packet deformatter 309, and an E-VSB dataprocessor 310.

More specifically, the received data through a tuner inputs to thedemodulator 301 and the known data detector 303. The demodulator 301demodulates the tuned channel frequency so as to perform carrierrecovery and timing recovery, thereby generating a baseband signal.Then, the demodulator 301 outputs the generated baseband signal to theequalizer 302 and the known data detector 303. The equalizer 302compensates for any channel distortion included in the demodulatedsignal. Thereafter, the equalizer 302 outputs the processed signal tothe SISO decoder 304.

At this point, the known data detector 303 detects the known data symbolsequence inserted from the transmitting system from the input/outputdata of the demodulator 301 (i.e., the data prior to demodulation or thedata after demodulation). Then, the known data detector 303 outputs thedetected sequence to the demodulator 301 and the equalizer 302. When thedemodulator 301 uses the known data symbol sequence during the timingrecovery or the carrier recovery, the demodulating performance may beenhanced. Similarly, when the equalizer 302 uses the known data symbolsequence, the equalization performance may be enhanced.

The SISO decoder 304 receives the output of the equalizer 302 andperforms SISO decoding on the received data, which are then outputted tothe deinterleaver 305. The SISO decoder 304 feeds-back the SISO decodedresult to the equalizer 302 so as to enhance the equalizing performance.Hereinafter, the soft output and soft input error correction decodingoperation of the SISO decoder 304 will now be described in detail.

More specifically, in order to enhance the performance of the additionalerror correction decoding performed on the enhanced data by the E-VSBdata processor 310, the SISO decoder 304 outputs a soft decision valueon the enhanced data. Accordingly, the E-VSB data processor 310 receivessuch soft decision value so as to perform the additional errorcorrection decoding process. In other words, the E-VSB data processor310 performs the additional error correction decoding process on thesoft-decided enhanced data. A Reed-Solomon (RS) decoder, a low densityparity check code (LDPC) decoder or a turbo decoder may be used as theerror correction decoder.

Meanwhile, the E-VSB convolutional encoder 113 of FIG. 1 and the E-VSBsymbol processor 209 of FIG. 2 perform encoding at a ½ coding rate(i.e., ½-rate coding) on the enhanced data in the symbol domain. Herein,a convolutional encoder may be used for the ½-rate coding. Therefore,the SISO decoder 304 considers the ½-rate encoder and the trellisencoder as a single encoder, thereby performing a SISO decoding processon the enhanced data. More specifically, in the E-VSB receiving system,concatenated encoding, in which a plurality of error correction codesare used, is performed on the enhanced data. At this point, the errorcorrection encoder of the E-VSB pre-processor may be used as an externalencoder, and the E-VSB convolutional encoder (or the E-VSB symbolprocessor) and the trellis encoder may be used as an internal encoder.

Therefore, in the digital broadcast receiving system, in order tomaximize the coding performance of the external code when decoding suchconcatenated codes, a soft decision value should be outputted from thedecoder of the internal code. For this reason, it is preferable that theSISO decoder 304 outputs a soft decision value of the enhanced data andnot a hard decision value. The algorithm for outputting the softdecision value on the convolution-coded enhanced data includes a softoutput Viterbi algorithm (SOVA) and a maximum a posteriori (MAP)algorithm. Herein, in light of symbol errors, the MAP algorithm has abetter performance. However, the MAP algorithm is disadvantageous inthat an optimum MAP algorithm requires probabilities (or likelihood) tobe calculated in an exponential domain and noise dispersion withinchannels to be estimated. Among many MAP algorithms, a suboptimum softoutput algorithm (SSA) shows the least decrease in performance,calculates probabilities (or likelihood) in a log domain, and does notrequire any estimation of noise dispersion.

In the digital broadcast transmitting system shown in FIG. 1 and FIG. 2,a ½-rate coding process is performed on 1-bit units of the enhanced datathrough the ½-rate encoder of the E-VSB convolutional encoder (or theE-VSB symbol processor). The ½-rate coded data are then trellis-encodedby the trellis encoder at a coding rate of ⅔. In other words, a codingprocess is performed at a coding rate of ⅓ on the enhanced data. A 1-bitunit of the enhanced data is encoded to 3 bits, thereby beingtransmitted as an 8-level VSB symbol. More specifically, the enhanceddata coded to 3-bit units are mapped as a VSB symbol among −7, −5, −3,−1, +1, +3, +5, and +7.

The SISO decoder 304 considers the ½-rate encoder and the trellisencoder as a single encoder, thereby performing a decoding process so asto output a log likelihood ratio (LLR), as shown in Equation 1 below, asthe soft decision value.

$\begin{matrix}{{L\; L\; R} = {{Log}\frac{\Pr\left( {d_{k} = {1/{observation}}} \right)}{\Pr\left( {d_{k} = {0/{observation}}} \right)}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Herein, observation represents an input sequence of the SISO decoder304, and the numerator and the denominator may be inversed and defined.Also, d_(k) indicates an input of the ½-rate encoder, and LLR representsa log value of a ratio between a value of the likelihood of d_(k) being1 and a value of the likelihood of d_(k) being 0. For example, when thelikelihood of d_(k) being 1 is 0.7, and when the likelihood of d_(k)being 0 is 0.3, the LLR value is equal to Log(0.7/0.3). Morespecifically, in Equation 1, if the LLR value corresponds to a positivenumber, this indicates that the likelihood (or probability) of thecurrent decoded enhanced data being equal to ‘1’ is high. Conversely, ifthe LLR value corresponds to a negative number, this indicates that thelikelihood (or probability) of the current decoded enhanced data beingequal to ‘0’ is high.

The SISO decoder 304 outputs a soft decision value with respect to theenhanced data symbol. On the other hand, the SISO decoder 304 outputs ahard decision value by using a trellis decoding algorithm, such as ageneral Viterbi decoder, with respect to the main data symbol and theknown data symbol. Furthermore, the E-VSB symbol processor considers theRS parity byte and the MPEG header byte, which have been added to theenhanced data packet by the transmitting system, as a main data symboland, therefore, does not perform coding at a ½ coding rate. For thisreason, the SISO decoder 304 outputs a hard decision value by using atrellis decoding algorithm, such as a general Viterbi decoder.

The deinterleaver 305 performs a deinterleaving process, whichcorresponds to the inverse operation of the data interleaver of thetransmitting system, on the output of the SISO decoder 304 and thenoutputs the processed data to the RS decoder/non-systematic RS parityremover 306. If the received data corresponds to the main data packet,the RS decoder/non-systematic RS parity remover 306 RS-decodes thereceived data. Alternatively, if the received data corresponds to theenhanced data packet, the RS decoder/non-systematic RS parity remover306 removes the non-systematic RS parity byte from the received data.Thereafter, the processed data are outputted to the derandomizer 307.

The derandomizer 307 receives the output of the RSdecoder/non-systematic RS parity remover 306 and generates a pseudorandom data byte identical to that of the randomizer included in thetransmitting system. Thereafter, the derandomizer 307 performs a bitwiseexclusive OR (XOR) operation on the generated pseudo random data byte,thereby inserting the MPEG synchronization bytes to the beginning ofeach packet so as to output the data in 188-byte main data packet units.The output data of the derandomizer 307 are outputted to the main MPEGdecoder (not shown) and also outputted to the main data packet remover308 at the same time.

However, it is difficult to perform a bitwise exclusive OR (XOR)operation between the soft decision value of the enhanced data bit andthe pseudo random bit. Accordingly, as described above, a hard decisionis performed on the data outputted to the main MPEG decoder inaccordance with the soft decision value of the coder. Thereafter, a XORoperation is performed between the hard decided output data and thepseudo random bit. More specifically, when the soft decision value is apositive number, the output data are decided as ‘1’, and when the softdecision value is a negative number, the output data are decided as ‘0’.And, a XOR operation is performed between such decision value and thepseudo random bit.

In the E-VSB data processor 310 of FIG. 3, a soft decision is needed inorder to enhance the performance when decoding the error correctioncode. Therefore, the derandomizer 307 creates a separate output withrespect to the enhanced data and outputs the newly created output to themain data packet remover 308. For example, when an XOR operation isperformed between the pseudo random bit and the soft decision value ofthe enhanced data bit, and when the pseudo random bit is equal to ‘1’,the derandomizer 307 changes the code of the soft decision value andthen outputs the changed code. On the other hand, if the pseudo randombit is equal to ‘0’, the derandomizer 307 outputs the soft decisionvalue without any change in the code.

If the pseudo random bit is equal to ‘1’ as described above, the code ofthe soft decision value is changed because, when an XOR operation isperformed between the pseudo random bit and the input data in therandomizer of the transmitter, and when the pseudo random bit is equalto ‘1’, the code of the output data bit becomes the opposite of theinput data (i.e., 0 XOR 1=1 and 1 XOR 0=0). More specifically, if thepseudo random bit generated from the derandomizer 307 is equal to ‘1’,and when an XOR operation is performed on the hard decision value of theenhanced data bit, the XOR-operated value becomes the opposite value ofthe hard decision value. Therefore, when the soft decision value isoutputted, a code opposite to that of the soft decision value isoutputted.

The main data packet remover 308 only obtains and outputs the softdecision value of the enhanced data packet from the output of thederandomizer 307. More specifically, the main data packet remover 308removes the 188-byte unit main data packet from the output of thederandomizer 307. Then, the main data packet remover 308 only obtainsthe soft decision value of the enhanced data packet and outputs theobtained value to the E-VSB packet deformatter 309.

The E-VSB packet deformatter 309 removes the MPEG header from the outputdata so as to obtain a 184-byte packet. Herein, the MPEG header has aPID for the enhanced data, which have been inserted by the transmittingsystem so as to be differentiated from the main data packet. Such184-byte data packets are grouped to form a group having a predeterminedsize. Thereafter, the known data that have been inserted for thedemodulation and equalization by the transmitting system are removedfrom a predetermined place (or position). The output of the E-VSB packetformatter 309 is inputted to the E-VSB data processor 310.

The E-VSB data processor 310 performs deinterleaving and decoding of theerror correction code with respect to the enhanced data that aresoft-decided and outputted. In other words, the E-VSB data processor 310performs an inverse operation of the E-VSB pre-processor of thetransmitting system. In the E-VSB pre-processor of the E-VSBtransmitting system, additional error correction coding, interleaving,and byte expansion processes are performed on the enhanced data. Herein,the byte expansion process is performed by inserting null bits or byrepeating input bits. Therefore, the E-VSB data processor 310 removesthe null bits or the repetition bits, which have been inserted by theE-VSB pro-processor for the byte expansion process, from thesoft-decided enhanced data. Thereafter, a deinterleaving process and aerror correction code decoding process are performed so as to output thefinally processed enhanced data.

FIG. 4 illustrates a block diagram showing the structure of a digitalbroadcast receiver according to an embodiment of the present invention.Referring to FIG. 4, the digital broadcast receiver includes a tuner401, a demodulating unit 402, a demultiplexer 403, an audio decoder 404,a video decoder 405, a native TV application manager 406, a channelmanager 407, a channel map 408, a first memory 409, a data decoder 410,a second memory 411, a system manager 412, a data broadcastingapplication manager 413, a storage controller 414, and a third memory415. Herein, the third memory 415 is a mass storage device, such as ahard disk drive (HDD) or a memory chip. The tuner 401 tunes a frequencyof a specific channel through any one of an antenna, cable, andsatellite. Then, the tuner 401 down-converts the tuned frequency to anintermediate frequency (IF), which is then outputted to the demodulatingunit 402. At this point, the tuner 401 is controlled by the channelmanager 407. Additionally, the result and strength of the broadcastsignal of the tuned channel are also reported to the channel manager407. The data that are being received by the frequency of the tunedspecific channel include main data, enhanced data, and table data fordecoding the main data and enhanced data.

In the embodiment of the present invention, examples of the enhanceddata may include data provided for data service, such as Javaapplication data, HTML application data, XML data, and so on. The dataprovided for such data services may correspond either to a Java classfile for the Java application, or to a directory file designatingpositions (or locations) of such files. Furthermore, such data may alsocorrespond to an audio file and/or a video file used in eachapplication. The data services may include weather forecast services,traffic information services, stock information services, servicesproviding information quiz programs providing audience participationservices, real time poll, user interactive education programs, gamingservices, services providing information on soap opera (or TV series)synopsis, characters, original sound track, filing sites, servicesproviding information on past sports matches, profiles andaccomplishments of sports players, product information and productordering services, services providing information on broadcast programsby media type, airing time, subject, and so on. The types of dataservices described above are only exemplary and are not limited only tothe examples given herein. Furthermore, depending upon the embodiment ofthe present invention, the enhanced data may correspond to meta data.For example, the meta data use the XML application so as to betransmitted through a DSM-CC protocol.

The demodulating unit 402 performs VSB-demodulation and channelequalization on the signal being outputted from the tuner 401, therebyidentifying the main data and the enhanced data. Thereafter, theidentified main data and enhanced data are outputted in TS packet units.An example of the demodulating unit 402 is shown in FIG. 3. Thedemodulating unit shown in FIG. 3 is merely exemplary and the scope ofthe present invention is not limited to the example set forth herein. Inthe embodiment given as an example of the present invention, only theenhanced data packet outputted from the demodulating unit 402 isinputted to the demultiplexer 403. In this case, the main data packet isinputted to another demultiplexer (not shown) that processes main datapackets. Herein, the storage controller 414 is also connected to theother demultiplexer in order to store the main data after processing themain data packets. The demultiplexer of the present invention may alsobe designed to process both enhanced data packets and main data packetsin a single demultiplexer.

The storage controller 414 is interfaced with the demultipelxer so as tocontrol instant recording, reserved (or pre-programmed) recording, timeshift, and so on of the enhanced data and/or main data. For example,when one of instant recording, reserved (or pre-programmed) recording,and time shift is set and programmed in the receiving system (orreceiver) shown in FIG. 4, the corresponding enhanced data and/or maindata that are inputted to the demultiplexer are stored in the thirdmemory 415 in accordance with the control of the storage controller 414.The third memory 415 may be described as a temporary storage area and/ora permanent storage area. Herein, the temporary storage area is used forthe time shifting function, and the permanent storage area is used for apermanent storage of data according to the user's choice (or decision).

When the data stored in the third memory 415 need to be reproduced (orplayed), the storage controller 414 reads the corresponding data storedin the third memory 415 and outputs the read data to the correspondingdemultiplexer (e.g., the enhanced data are outputted to thedemultiplexer 403 shown in FIG. 4). At this point, according to theembodiment of the present invention, since the storage capacity of thethird memory 415 is limited, the compression encoded enhanced dataand/or main data that are being inputted are directly stored in thethird memory 415 without any modification for the efficiency of thestorage capacity. In this case, depending upon the reproduction (orreading) command, the data read from the third memory 415 pass troughthe demultiplexer so as to be inputted to the corresponding decoder,thereby being restored to the initial state.

The storage controller 414 may control the reproduction (or play),fast-forward, rewind, slow motion, instant replay functions of the datathat are already stored in the third memory 415 or presently beingbuffered. Herein, the instant replay function corresponds to repeatedlyviewing scenes that the viewer (or user) wishes to view once again. Theinstant replay function may be performed on stored data and also on datathat are currently being received in real time by associating theinstant replay function with the time shift function. If the data beinginputted correspond to the analog format, for example, if thetransmission mode is NTSC, PAL, and so on, the storage controller 414compression encodes the inputted data and stored the compression-encodeddata to the third memory 415. In order to do so, the storage controller414 may include an encoder, wherein the encoder may be embodied as oneof software, middleware, and hardware. Herein, an MPEG encoder may beused as the encoder according to an embodiment of the present invention.The encoder may also be provided outside of the storage controller 414.

Meanwhile, in order to prevent illegal duplication (or copies) of theinput data being stored in the third memory 415, the storage controller414 scrambles the input data and stores the scrambled data in the thirdmemory 415. Accordingly, the storage controller 414 may include ascramble algorithm for scrambling the data stored in the third memory415 and a descramble algorithm for descrambling the data read from thethird memory 415. Herein, the definition of scramble includesencryption, and the definition of descramble includes decryption. Thescramble method may include using an arbitrary key (e.g., control word)to modify a desired set of data, and also a method of mixing signals.

Meanwhile, the demultiplexer 403 receives the real-time data outputtedfrom the demodulating unit 402 or the data read from the third memory415 and demultiplexes the received data. In the example given in thepresent invention, the demultiplexer 403 performs demultiplexing on theenhanced data packet. Therefore, in the present invention, the receivingand processing of the enhanced data will be described in detail. Itshould also be noted that a detailed description of the processing ofthe main data will be omitted for simplicity starting from thedescription of the demultiplexer 403 and the subsequent elements.

The demultiplexer 403 demultiplexes enhanced data and program specificinformation/program and system information protocol (PSI/PSIP) tablesfrom the enhanced data packet inputted in accordance with the control ofthe data decoder 410. Thereafter, the demultiplexed enhanced data andPSI/PSIP tables are outputted to the data decoder 410 in a sectionformat. In order to extract the enhanced data from the channel throughwhich enhanced data are transmitted and to decode the extracted enhanceddata, system information is required. Such system information may alsobe referred to as service information. The system information mayinclude channel information, event information, etc. In the embodimentof the present invention, the PSI/PSIP tables are applied as the systeminformation. However, the present invention is not limited to theexample set forth herein. More specifically, regardless of the name, anyprotocol transmitting system information in a table format may beapplied in the present invention.

The PSI table is an MPEG-2 system standard defined for identifying thechannels and the programs. The PSIP table is an advanced televisionsystems committee (ATSC) standard that can identify the channels and theprograms. The PSI table may include a program association table (PAT), aconditional access table (CAT), a program map table (PMT), and a networkinformation table (NIT). Herein, the PAT corresponds to specialinformation that is transmitted by a data packet having a PID of ‘0’.The PAT transmits PID information of the PMT and PID information of theNIT corresponding to each program. The CAT transmits information on apaid broadcast system used by the transmitting system. The PMT transmitsPID information of a transport stream (TS) packet, in which programidentification numbers and individual bit sequences of video and audiodata configuring the corresponding program are transmitted, and the PIDinformation, in which PCR is transmitted. The NIT transmits informationof the actual transmission network.

The PSIP table may include a virtual channel table (VCT), a system timetable (STT), a rating region table (RRT), an extended text table (ETT),a direct channel change table (DCCT), an event information table (EIT),and a master guide table (MGT). The VCT transmits information on virtualchannels, such as channel information for selecting channels andinformation such as packet identification (PID) numbers for receivingthe audio and/or video data. More specifically, when the VCT is parsed,the PID of the audio/video data of the broadcast program may be known.Herein, the corresponding audio/video data are transmitted within thechannel along with the channel name and the channel number. The STTtransmits information on the current data and timing information. TheRRT transmits information on region and consultation organs for programratings. The ETT transmits additional description of a specific channeland broadcast program. The EIT transmits information on virtual channelevents (e.g., program title, program start time, etc.). The DCCT/DCCSCTtransmits information associated with automatic (or direct) channelchange. And, the MGT transmits the versions and PID information of theabove-mentioned tables included in the PSIP.

Each of the above-described tables included in the PSI/PSIP isconfigured of a basic unit referred to as a “section”, and a combinationof one or more sections forms a table. For example, the VCT may bedivided into 256 sections. Herein, one section may include a pluralityof virtual channel information. However, a single set of virtual channelinformation is not divided into two or more sections. At this point, thereceiving system may parse and decode the data for the data service thatare transmitting by using only the tables included in the PSI, or onlythe tables included in the PISP, or a combination of tables included inboth the PSI and the PSIP. In order to parse and decode the data for thedata service, at least one of the PAT and PMT included in the PSI, andthe VCT included in the PSIP is required. For example, the PAT mayinclude the system information for transmitting the data correspondingto the data service, and the PID of the PMT corresponding to the dataservice data (or program number). The PMT may include the PID of the TSpacket used for transmitting the data service data. The VCT may includeinformation on the virtual channel for transmitting the data servicedata, and the PID of the TS packet for transmitting the data servicedata.

Meanwhile, depending upon the embodiment of the present invention, aDVB-SI may be applied instead of the PSIP. The DVB-SI may include anetwork information table (NIT), a service description table (SDT), anevent information table (EIT), and a time and data table (TDT). TheDVB-SI may be used in combination with the above-described PSI. Herein,the NIT divides the services corresponding to particular networkproviders by specific groups. The NIT includes all tuning informationthat are used during the IRD set-up. The NIT may be used for informingor notifying any change in the tuning information. The SDT includes theservice name and different parameters associated with each servicecorresponding to a particular MPEG multiplex. The EIT is used fortransmitting information associated with all events occurring in theMPEG multiplex. The EIT includes information on the current transmissionand also includes information selectively containing differenttransmission streams that may be received by the IRD. And, the TDT isused for updating the clock included in the IRD.

Furthermore, three selective SI tables (i.e., a bouquet associate table(BAT), a running status table (RST), and a stuffing table (ST)) may alsobe included. More specifically, the bouquet associate table (BAT)provides a service grouping method enabling the IRD to provide servicesto the viewers. Each specific service may belong to at least one‘bouquet’ unit. A running status table (RST) section is used forpromptly and instantly updating at least one event execution status. Theexecution status section is transmitted only once at the changing pointof the event status. Other SI tables are generally transmitted severaltimes. The stuffing table (ST) may be used for replacing or discarding asubsidiary table or the entire SI tables.

In the present invention, the enhanced data included in the payloadwithin the TS packet consist of a digital storage media-command andcontrol (DSM-CC) section format. However, the TS packet including thedata service data may correspond either to a packetized elementarystream (PES) type or to a section type. More specifically, either thePES type data service data configure the TS packet, or the section typedata service data configure the TS packet. The TS packet configured ofthe section type data will be given as the example of the presentinvention. At this point, the data service data are includes in thedigital storage media-command and control (DSM-CC) section. Herein, theDSM-CC section is then configured of a 188-byte unit TS packet.

Furthermore, the packet identification of the TS packet configuring theDSM-CC section is included in a data service table (DST). Whentransmitting the DST, ‘0x95’ is assigned as the value of a stream typefield included in the service location descriptor of the PMT or the VCT.More specifically, when the PMT or VCT stream type field value is‘0x95’, the receiving system may acknowledge that data broadcastingincluding enhanced data (i.e., the enhanced data) is being received. Atthis point, the enhanced data may be transmitted by a data carouselmethod. The data carousel method corresponds to repeatedly transmittingidentical data on a regular basis.

At this point, according to the control of the data decoder 410, thedemultiplexer 403 performs section filtering, thereby discardingrepetitive sections and outputting only the non-repetitive sections tothe data decoder 410. The demultiplexer 403 may also output only thesections configuring desired tables (e.g., VCT) to the data decoder 410by section filtering. Herein, the VCT may include a specific descriptorfor the enhanced data. However, the present invention does not excludethe possibilities of the enhanced data being included in other tables,such as the PMT. The section filtering method may include a method ofverifying the PID of a table defined by the MGT, such as the VCT, priorto performing the section filtering process. Alternatively, the sectionfiltering method may also include a method of directly performing thesection filtering process without verifying the MGT, when the VCTincludes a fixed PID (i.e., a base PID). At this point, thedemultiplexer 403 performs the section filtering process by referring toa table_id field, a version_number field, a section_number field, etc.

As described above, the method of defining the PID of the VCT broadlyincludes two different methods. Herein, the PID of the VCT is a packetidentifier required for identifying the VCT from other tables. The firstmethod consists of setting the PID of the VCT so that it is dependent tothe MGT. In this case, the receiving system cannot directly verify theVCT among the many PSI and/or PSIP tables. Instead, the receiving systemmust check the PID defined in the MGT in order to read the VCT. Herein,the MGT defines the PID, size, version number, and so on, of diversetables. The second method consists of setting the PID of the VCT so thatthe PID is given a base PID value (or a fixed PID value), thereby beingindependent from the MGT. In this case, unlike in the first method, theVCT according to the present invention may be identified without havingto verify every single PID included in the MGT. Evidently, an agreementon the base PIP must be previously made between the transmitting systemand the receiving system.

Meanwhile, in the embodiment of the present invention, the demultiplexer403 may output only an application information table (AIT) to the datadecoder 410 by section filtering. The AIT includes information on anapplication being operated in the receiver for the data service. The AITmay also be referred to as an XAIT, and an AMT. Therefore, any tableincluding application information may correspond to the followingdescription. When the AIT is transmitted, a value of ‘0x05’ may beassigned to a stream type field of the PMT. The AIT may includeapplication information, such as application name, application version,application priority, application ID, application status (i.e.,auto-start, user-specific settings, kill, etc.), application type (i.e.,Java or HTML), position (or location) of stream including applicationclass and data files, application platform directory, and location ofapplication icon.

In the method for detecting application information for the data serviceby using the AIT, component_tag, original_network_id,transport_stream_id, and service_id fields may be used for detecting theapplication information. The component_tag field designates anelementary stream carrying a DSI of a corresponding object carousel. Theoriginal_network_id field indicates a DVB-SI original_network_id of theTS providing transport connection. The transport_stream_id fieldindicates the MPEG TS of the TS providing transport connection, and theservice_id field indicates the DVB-SI of the service providing transportconnection. Information on a specific channel may be obtained by usingthe original_network_id field, the transport_stream_id field, and theservice_id field. The data service data, such as the application data,detected by using the above-described method may be stored in the secondmemory 411 by the data decoder 410.

The data decoder 410 parses the DSM-CC section configuring thedemultiplexed enhanced data. Then, the enhanced data corresponding tothe parsed result are stored as a database in the second memory 411. Thedata decoder 410 groups a plurality of sections having the same tableidentification (table_id) so as to configure a table, which is thenparsed. Thereafter, the parsed result is stored as a database in thesecond memory 411. At this point, by parsing data and/or sections, thedata decoder 410 reads all of the remaining actual section data that arenot section-filtered by the demultiplexer 403. Then, the data decoder410 stores the read data to the second memory 411. The second memory 411corresponds to a table and data carousel database storing systeminformation parsed from tables and enhanced data parsed from the DSM-CCsection. Herein, a table_id field, a section_number field, and alast_section_number field included in the table may be used to indicatewhether the corresponding table is configured of a single section or aplurality of sections. For example, TS packets having the PID of the VCTare grouped to form a section, and sections having table identifiersallocated to the VCT are grouped to form the VCT.

When the VCT is parsed, information on the virtual channel to whichenhanced data are transmitted may be obtained. The obtained applicationidentification information, service component identificationinformation, and service information corresponding to the data servicemay either be stored in the second memory 411 or be outputted to thedata broadcasting application manager 413. In addition, reference may bemade to the application identification information, service componentidentification information, and service information in order to decodethe data service data. Alternatively, such information may also preparethe operation of the application program for the data service.Furthermore, the data decoder 410 controls the demultiplexing of thesystem information table, which corresponds to the information tableassociated with the channel and events. Thereafter, an A.V PID list maybe transmitted to the channel manager 407.

The channel manager 407 may refer to the channel map 408 in order totransmit a request for receiving system-related information data to thedata decoder 410, thereby receiving the corresponding result. Inaddition, the channel manager 407 may also control the channel tuning ofthe tuner 401. Furthermore, the channel manager 407 may directly controlthe demultiplexer 403, so as to set up the A/V PID, thereby controllingthe audio decoder 404 and the video decoder 405. The audio decoder 404and the video decoder 405 may respectively decode and output the audiodata and video data demultiplexed from the main data packet.Alternatively, the audio decoder 404 and the video decoder 405 mayrespectively decode and output the audio data and video datademultiplexed from the enhanced data packet. Meanwhile, when theenhanced data include data service data, and also audio data and videodata, it is apparent that the audio data and video data demultiplexed bythe demultiplexer 403 are respectively decoded by the audio decoder 404and the video decoder 405. For example, an audio-coding (AC)-3 decodingalgorithm may be applied to the audio decoder 404, and a MPEG-2 decodingalgorithm may be applied to the video decoder 405.

Meanwhile, the native TV application manager 406 operates a nativeapplication program stored in the first memory 409, thereby performinggeneral functions such as channel change. The native application programrefers to software stored in the receiving system upon shipping of theproduct. More specifically, when a user request (or command) istransmitted to the receiving system through a user interface (UI), thenative TV application manger 406 displays the user request on a screenthrough a graphic user interface (GUI), thereby responding to the user'srequest. The user interface receives the user request through an inputdevice, such as a remote controller, a key pad, a jog controller, an atouch-screen provided on the screen, and then outputs the received userrequest to the native TV application manager 406 and the databroadcasting application manager 413. Furthermore, the native TVapplication manager 406 controls the channel manager 407, therebycontrolling channel-associated, such as the management of the channelmap 408, and controlling the data decoder 410. The native TV applicationmanager 406 also controls the GUI of the overall receiving system,thereby storing the user request and status of the receiving system inthe first memory 409 and restoring the stored information.

The channel manager 407 controls the tuner 401 and the data decoder 410,so as to managing the channel map 408 so that it can respond to thechannel request made by the user. More specifically, channel manager 407sends a request to the data decoder 410 so that the tables associatedwith the channels that are to be tuned are parsed. The results of theparsed tables are reported to the channel manager 407 by the datadecoder 410. Thereafter, based on the parsed results, the channelmanager 407 updates the channel map 408 and sets up a PID in thedemultiplexer 403 for demultiplexing the tables associated with the dataservice data from the enhanced data.

The system manager 412 controls the booting of the receiving system byturning the power on or off. Then, the system manager 412 stores ROMimages (including downloaded software images) in the first memory 409.More specifically, the first memory 409 stores management programs suchas operating system (OS) programs required for managing the receivingsystem and also application program executing data service functions.The application program is a program processing the data service datastored in the second memory 411 so as to provide the user with the dataservice. If the data service data are stored in the second memory 411,the corresponding data service data are processed by the above-describedapplication program or by other application programs, thereby beingprovided to the user. The management program and application programstored in the first memory 409 may be updated or corrected to a newlydownloaded program. Furthermore, the storage of the stored managementprogram and application program is maintained without being deleted evenif the power of the system is shut down. Therefore, when the power issupplied the programs may be executed without having to be newlydownloaded once again.

The application program for providing data service according to thepresent invention may either be initially stored in the first memory 409upon the shipping of the receiving system, or be stored in the first 409after being downloaded. The application program for the data service(i.e., the data service providing application program) stored in thefirst memory 409 may also be deleted, updated, and corrected.Furthermore, the data service providing application program may bedownloaded and executed along with the data service data each time thedata service data are being received.

When a data service request is transmitted through the user interface,the data broadcasting application manager 413 operates the correspondingapplication program stored in the first memory 409 so as to process therequested data, thereby providing the user with the requested dataservice. And, in order to provide such data service, the databroadcasting application manager 413 supports the graphic user interface(GUI). Herein, the data service may be provided in the form of text (orshort message service (SMS)), voice message, still image, and movingimage. The data broadcasting application manager 413 may be providedwith a platform for executing the application program stored in thefirst memory 409. The platform may be, for example, a Java virtualmachine for executing the Java program. Hereinafter, an example of thedata broadcasting application manager 413 executing the data serviceproviding application program stored in the first memory 409, so as toprocess the data service data stored in the second memory 411, therebyproviding the user with the corresponding data service will now bedescribed in detail.

Assuming that the data service corresponds to a traffic informationservice, the data service according to the present invention is providedto the user of a receiver that is not equipped with an electronic mapand/or a GPS system in the form of at least one of a text (or shortmessage service (SMS)), a voice message, a graphic message, a stillimage, and a moving image. In this case, is a GPS module is mounted onthe receiving system shown in FIG. 4, the GPS module receives satellitesignals transmitted from a plurality of low earth orbit satellites andextracts the current position (or location) information (e.g.,longitude, latitude, altitude), thereby outputting the extractedinformation to the data broadcasting application manager 413.

At this point, it is assumed that the electronic map includinginformation on each link and nod and other diverse graphic informationare stored in one of the second memory 411, the first memory 409, andanother memory that is not shown. More specifically, according to therequest made by the data broadcasting application manager 413, the dataservice data stored in the second memory 411 are read and inputted tothe data broadcasting application manager 413. The data broadcastingapplication manager 413 translates (or deciphers) the data service dataread from the second memory 411, thereby extracting the necessaryinformation according to the contents of the message and/or a controlsignal.

FIG. 5 illustrates a block diagram showing the structure of a digitalbroadcast (or television) receiver according to another embodiment ofthe present invention. Referring to FIG. 5, the digital broadcastreceiver includes a tuner 501, a demodulating unit 502, a demultiplexer503, a first descrambler 504, an audio decoder 505, a video decoder 506,a second descrambler 507, an authentication unit 508, a native TVapplication manager 509, a channel manager 510, a channel map 511, afirst memory 512, a data decoder 513, a second memory 514, a systemmanager 515, a data broadcasting application manager 516, a storagecontroller 517, a third memory 518, and a telecommunication module 519.Herein, the third memory 518 is a mass storage device, such as a harddisk drive (HDD) or a memory chip. Also, during the description of thedigital broadcast (or television) receiver shown in FIG. 5, thecomponents that are identical to those of the digital broadcast receiverof FIG. 4 will be omitted for simplicity.

As described above, in order to provide services for preventing illegalduplication (or copies) or illegal viewing of the enhanced data and/ormain data that are transmitted by using a broadcast network, and toprovide paid broadcast services, the transmitting system may generallyscramble and transmit the broadcast contents. Therefore, the receivingsystem needs to descramble the scrambled broadcast contents in order toprovide the user with the proper broadcast contents. Furthermore, thereceiving system may generally be processed with an authenticationprocess with an authentication means before the descrambling process.Hereinafter, the receiving system including an authentication means anda descrambling means according to an embodiment of the present inventionwill now be described in detail.

According to the present invention, the receiving system may be providedwith a descrambling means receiving scrambled broadcasting contents andan authentication means authenticating for verifying) whether thereceiving system is entitled to receive the descrambled contents.Hereinafter, the descrambling means will be referred to as first andsecond descramblers 504 and 507, and the authentication means will bereferred to as an authentication unit 50B. Such naming of thecorresponding components is merely exemplary and is not limited to theterms suggested in the description of the present invention. Forexample, the units may also be referred to as a decryptor. Although FIG.5 illustrates an example of the descramblers 504 and 507 and theauthentication unit 508 being provided inside the receiving system, eachof the descramblers 504 and 507 and the authentication unit 508 may alsobe separately provided in an internal or external module. Herein, themodule may include a slot type, such as a SD or CF memory, a memorystick type, a USB type, and so on, and may be detachably fixed to thereceiving system.

As described above, when the authentication process is performedsuccessfully by the authentication unit 508, the scrambled broadcastingcontents are descrambled by the descramblers 504 and 507, thereby beingprovided to the user. At this point, a variety of the authenticationmethod and descrambling method may be used herein. However, an agreementon each corresponding method should be made between the receiving systemand the transmitting system. Hereinafter, the authentication anddescrambling methods will now be described, and the description ofidentical components or process steps will be omitted for simplicity.

The receiving system including the authentication unit 508 and thedescramblers 504 and 507 will now be described in detail. The receivingsystem receives the scrambled broadcasting contents through the tuner501 and the demodulating unit 502. Then, the system manager 515 decideswhether the received broadcasting contents have been scrambled. Herein,the demodulating unit 502 may be included as a demodulating meansaccording to an embodiment of the present invention as described in FIG.3. However, the present invention is not limited to the examples givenin the description set forth herein. If the system manager 515 decidesthat the received broadcasting contents have been scrambled, then thesystem manager 515 controls the system to operate the authenticationunit 508. As described above, the authentication unit 50B performs anauthentication process in order to decide whether the receiving systemaccording to the present invention corresponds to a legitimate hostentitled to receive the paid broadcasting service. Herein, theauthentication process may vary in accordance with the authenticationmethods.

For example, the authentication unit 508 may perform the authenticationprocess by comparing an IP address of an IP datagram within the receivedbroadcasting contents with a specific address of a corresponding host.At this point, the specific address of the corresponding receivingsystem (or host) may be a MAC address. More specifically, theauthentication unit 508 may extract the IP address from the decapsulatedIP datagram, thereby obtaining the receiving system information that ismapped with the IP address. At this point, the receiving system shouldbe provided, in advance, with information (e.g., a table format) thatcan map the IP address and the receiving system information.Accordingly, the authentication unit 508 performs the authenticationprocess by determining the conformity between the address of thecorresponding receiving system and the system information of thereceiving system that is mapped with the IP address. In other words, ifthe authentication unit 508 determines that the two types of informationconform to one another, then the authentication unit 508 determines thatthe receiving system is entitled to receive the correspondingbroadcasting contents.

In another example, standardized identification information is definedin advance by the receiving system and the transmitting system. Then,the identification information of the receiving system requesting thepaid broadcasting service is transmitted by the transmitting system.Thereafter, the receiving system determines whether the receivedidentification information conforms with its own unique identificationnumber, so as to perform the authentication process. More specifically,the transmitting system creates a database for storing theidentification information (or number) of the receiving systemrequesting the paid broadcasting service. Then, if the correspondingbroadcasting contents are scrambled, the transmitting system includesthe identification information in the EMM, which is then transmitted tothe receiving system.

If the corresponding broadcasting contents are scrambled, messages(e.g., entitlement control message (ECM), entitlement management message(EMM)), such as the CAS information, mode information, message positioninformation, that are applied to the scrambling of the broadcastingcontents are transmitted through a corresponding data header or anotherdata packet. The ECM may include a control word (CW) used for scramblingthe broadcasting contents. At this point, the control word may beencoded with an authentication key. The EMM may include anauthentication key and entitlement information of the correspondingdata. Herein, the authentication key may be encoded with areceiver-specific distribution key. In other words, assuming that theenhanced data are scrambled by using the control word, and that theauthentication information and the descrambling information aretransmitted from the transmitting system, the transmitting systemencodes the CW with the authentication key and, then, includes theencoded CW in the entitlement control message (ECM), which is thentransmitted to the receiving system. Furthermore, the transmittingsystem includes the authentication key used for encoding the CW and theentitlement to receive data (or services) of the receiving system (i.e.,a standardized serial number of the receiving system that is entitled toreceive the corresponding broadcasting service or data) in theentitlement management message (EMM), which is then transmitted to thereceiving system.

Accordingly, the authentication unit 508 of the receiving systemextracts the identification information of the receiving system and theidentification information included in the EMM of the broadcastingservice that is being received. Then, the authentication unit 508determines whether the identification information conform to each other,so as to perform the authentication process. More specifically, if theauthentication unit 508 determines that the information conform to eachother, then the authentication unit 508 eventually determines that thereceiving system is entitled to receive the request broadcastingservice.

In yet another example, the authentication unit 508 of the receivingsystem may be detachably fixed to an external module. In this case, thereceiving system is interfaced with the external module through a commoninterface (CI). In other words, the external module may receive the datascrambled by the receiving system through the common interface, therebyperforming the descrambling process of the received data. Alternatively,the external module may also transmit only the information required forthe descrambling process to the receiving system. The common interfaceis configured on a physical layer and at least one protocol layer.Herein, in consideration of any possible expansion of the protocol layerin a later process, the corresponding protocol layer may be configuredto have at least one layer that can each provide an independentfunction.

The external module may either consist of a memory or card havinginformation on the key used for the scrambling process and otherauthentication information but not including any descrambling function,or consist of a card having the above-mentioned key information andauthentication information and including the descrambling function. Boththe receiving system and the external module should be authenticated inorder to provide the user with the paid broadcasting service provided(or transmitted) from the transmitting system. Therefore, thetransmitting system can only provide the corresponding paid broadcastingservice to the authenticated pair of receiving system and externalmodule.

Additionally, an authentication process should also be performed betweenthe receiving system and the external module through the commoninterface. More specifically, the module may communicate with the systemmanager 515 included in the receiving system through the commoninterface, thereby authenticating the receiving system. Alternatively,the receiving system may authenticate the module through the commoninterface. Furthermore, during the authentication process, the modulemay extract the unique ID of the receiving system and its own unique IDand transmit the extracted IDs to the transmitting system. Thus, thetransmitting system may use the transmitted ID values as informationdetermining whether to start the requested service or as paymentinformation. Whenever necessary, the system manager 515 transmits thepayment information to the remote transmitting system through thetelecommunication module 519.

The authentication unit 508 authenticates the corresponding receivingsystem and/or the external module. Then, if the authentication processis successfully completed, the authentication unit 508 certifies thecorresponding receiving system and/or the external module as alegitimate system and/or module entitled to receive the requested paidbroadcasting service. In addition, the authentication unit 508 may alsoreceive authentication-associated information from a mobiletelecommunications service provider to which the user of the receivingsystem is subscribed, instead of the transmitting system providing therequested broadcasting service. In this case, theauthentication-association information may either be scrambled by thetransmitting system providing the broadcasting service and, then,transmitted to the user through the mobile telecommunications serviceprovider, or be directly scrambled and transmitted by the mobiletelecommunications service provider. Once the authentication process issuccessfully completed by the authentication unit 508, the receivingsystem may descramble the scrambled broadcasting contents received fromthe transmitting system. At this point, the descrambling process isperformed by the first and second descramblers 504 and 507. Herein, thefirst and second descramblers 504 and 507 may be included in an internalmodule or an external module of the receiving system.

The receiving system is also provided with a common interface forcommunicating with the external module including the first and seconddescramblers 504 and 507, so as to perform the descrambling process.More specifically, the first and second descramblers 504 and 507 may beincluded in the module or in the receiving system in the form ofhardware, middleware or software. Herein, the descramblers 504 and 507may be included in any one of or both of the module and the receivingsystem. If the first and second descramblers 504 and 507 are providedinside the receiving system, it is advantageous to have the transmittingsystem (i.e., at least any one of a service provider and a broadcaststation) scramble the corresponding data using the same scramblingmethod.

Alternatively, if the first and second descramblers 504 and 507 areprovided in the external module, it is advantageous to have eachtransmitting system scramble the corresponding data using differentscrambling methods. In this case, the receiving system is not requiredto be provided with the descrambling algorithm corresponding to eachtransmitting system. Therefore, the structure and size of receivingsystem may be simplified and more compact. Accordingly, in this case,the external module itself may be able to provide CA functions, whichare uniquely and only provided by each transmitting systems, andfunctions related to each service that is to be provided to the user.The common interface enables the various external modules and the systemmanager 515, which is included in the receiving system, to communicatewith one another by a single communication method. Furthermore, sincethe receiving system may be operated by being connected with at leastone or more modules providing different services, the receiving systemmay be connected to a plurality of modules and controllers.

In order to maintain successful communication between the receivingsystem and the external module, the common interface protocol includes afunction of periodically checking the status of the oppositecorrespondent. By using this function, the receiving system and theexternal module is capable of managing the status of each oppositecorrespondent. This function also reports the user or the transmittingsystem of any malfunction that may occur in any one of the receivingsystem and the external module and attempts the recovery of themalfunction.

In yet another example, the authentication process may be performedthrough software. More specifically, when a memory card having CASsoftware downloaded, for example, and stored therein in advanced isinserted in the receiving system, the receiving system receives andloads the CAS software from the memory card so as to perform theauthentication process. In this example, the CAS software is read outfrom the memory card and stored in the first memory 512 of the receivingsystem. Thereafter, the CAS software is operated in the receiving systemas an application program. According to an embodiment of the presentinvention, the CAS software is mounted on (or stored) in a middlewareplatform and, then executed. A Java middleware will be given as anexample of the middleware included in the present invention. Herein, theCAS software should at least include information required for theauthentication process and also information required for thedescrambling process.

Therefore, the authentication unit 508 performs authentication processesbetween the transmitting system and the receiving system and alsobetween the receiving system and the memory card. At this point, asdescribed above, the memory card should be entitled to receive thecorresponding data and should include information on a normal receivingsystem that can be authenticated. For example, information on thereceiving system may include a unique number, such as a standardizedserial number of the corresponding receiving system. Accordingly, theauthentication unit 508 compares the standardized serial number includedin the memory card with the unique information of the receiving system,thereby performing the authentication process between the receivingsystem and the memory card.

If the CAS software is first executed in the Java middleware base, thenthe authentication between the receiving system and the memory card isperformed. For example, when the unique number of the receiving systemstored in the memory card conforms to the unique number of the receivingsystem read from the system manager 515, then the memory card isverified and determined to be a normal memory card that may be used inthe receiving system. At this point, the CAS software may either beinstalled in the first memory 512 upon the shipping of the presentinvention, or be downloaded to the first memory 512 from thetransmitting system or the module or memory card, as described above.Herein, the descrambling function may be operated by the databroadcasting application manger 516 as an application program.

Thereafter, the CAS software parses the EMM/ECM packets outputted fromthe demultiplexer 503, so as to verify whether the receiving system isentitled to receive the corresponding data, thereby obtaining theinformation required for descrambling (i.e., the CW) and providing theobtained CW to the descramblers 504 and 507. More specifically, the CASsoftware operating in the Java middleware platform first reads out theunique (or serial) number of the receiving system from the correspondingreceiving system and compares it with the unique number of the receivingsystem transmitted through the EMM, thereby verifying whether thereceiving system is entitled to receive the corresponding data. Once thereceiving entitlement of the receiving system is verified, thecorresponding broadcasting service information transmitted to the ECMand the entitlement of receiving the corresponding broadcasting serviceare used to verify whether the receiving system is entitled to receivethe corresponding broadcasting service. Once the receiving system isverified to be entitled to receive the corresponding broadcastingservice, the authentication key transmitted to the EMM is used to decode(or decipher) the encoded CW, which is transmitted to the ECM, therebytransmitting the decoded CW to the descramblers 504 and 507. Each of thedescramblers 504 and 507 uses the CW to descramble the broadcastingservice.

Meanwhile, the CAS software stored in the memory card may be expanded inaccordance with the paid service which the broadcast station is toprovide. Additionally, the CAS software may also include otheradditional information other than the information associated with theauthentication and descrambling. Furthermore, the receiving system maydownload the CAS software from the transmitting system so as to upgrade(or update) the CAS software originally stored in the memory card. Asdescribed above, regardless of the type of broadcast receiver, as longas an external memory interface is provided, the present invention mayembody a CAS system that can meet the requirements of all types ofmemory card that may be detachably fixed to the receiving system. Thus,the present invention may realize maximum performance of the receivingsystem with minimum fabrication cost, wherein the receiving system mayreceive paid broadcasting contents such as broadcast programs, therebyacknowledging and regarding the variety of the receiving system.Moreover, since only the minimum application program interface isrequired to be embodied in the embodiment of the present invention, thefabrication cost may be minimized, thereby eliminating themanufacturer's dependence on CAS manufacturers. Accordingly, fabricationcosts of CAS equipments and management systems may also be minimized.

Meanwhile, the descramblers 504 and 507 may be included in the moduleeither in the form of hardware or in the form of software. In this case,the scrambled data that being received are descrambled by the module andthen demodulated. Also, if the scrambled data that are being receivedare stored in the third memory 518, the received data may be descrambledand then stored, or stored in the memory at the point of being receivedand then descrambled later on prior to being played (or reproduced).Thereafter, in case scramble/descramble algorithms are provided in thestorage controller 517, the storage controller 517 scrambles the datathat are being received once again and then stores the re-scrambled datato the third memory 518.

In yet another example, the descrambled broadcasting contents(transmission of which being restricted) are transmitted through thebroadcasting network. Also, information associated with theauthentication and descrambling of data in order to disable thereceiving restrictions of the corresponding data are transmitted and/orreceived through the telecommunications module 519. Thus, the receivingsystem is able to perform reciprocal (or two-way) communication. Thereceiving system may either transmit data to the telecommunicationmodule within the transmitting system or be provided with the data fromthe telecommunication module within the transmitting system. Herein, thedata correspond to broadcasting data that are desired to be transmittedto or from the transmitting system, and also unique information (i.e.,identification information) such as a serial number of the receivingsystem or MAC address.

The telecommunication module 519 included in the receiving systemprovides a protocol required for performing reciprocal (or two-way)communication between the receiving system, which does not support thereciprocal communication function, and the telecommunication moduleincluded in the transmitting system. Furthermore, the receiving systemconfigures a protocol data unit (PDU) using a tag-length-value (TLV)coding method including the data that are to be transmitted and theunique information (or ID information). Herein, the tag field includesindexing of the corresponding PDU. The length field includes the lengthof the value field. And, the value field includes the actual data thatare to be transmitted and the unique number (e.g., identificationnumber) of the receiving system.

The receiving system may configure a platform that is equipped with theJava platform and that is operated after downloading the Javaapplication of the transmitting system to the receiving system throughthe network. In this case, a structure of downloading the PDU includingthe tag field arbitrarily defined by the transmitting system from astorage means included in the receiving system and then transmitting thedownloaded PDU to the telecommunication module 519 may also beconfigured. Also, the PDU may be configured in the Java application ofthe receiving system and then outputted to the telecommunication module519. The PDU may also be configured by transmitting the tag value, theactual data that are to be transmitted, the unique information of thecorresponding receiving system from the Java application and byperforming the TLV coding process in the receiving system. Thisstructure is advantageous in that the firmware of the receiving systemis not required to be changed even if the data (or application) desiredby the transmitting system is added.

The telecommunication module within the transmitting system eithertransmits the PDU received from the receiving system through a wirelessdata network or configures the data received through the network into aPDU which is transmitted to the host. At this point, when configuringthe PDU that is to be transmitted to the host, the telecommunicationmodule within the transmitting end may include unique information (e.g.,IP address) of the transmitting system which is located in a remotelocation. Additionally, in receiving and transmitting data through thewireless data network, the receiving system may be provided with acommon interface, and also provided with a WAP, CDMA 1×EV-DO, which canbe connected through a mobile telecommunication base station, such asCDMA and GSM, and also provided with a wireless LAN, mobile Internet,WiBro, WiMax, which can be connected through an access point. Theabove-described receiving system corresponds to the system that is notequipped with a telecommunication function. However, a receiving systemequipped with telecommunication function does not require thetelecommunication module 519.

The broadcasting data being transmitted and received through theabove-described wireless data network may include data required forperforming the function of limiting data reception. Meanwhile, thedemultiplexer 503 receives either the real-time data outputted from thedemodulating unit 502 or the data read from the third memory 518,thereby performing demultiplexing. In this embodiment of the presentinvention, the demultiplexer 503 performs demultiplexing on the enhanceddata packet. Similar process steps have already been described earlierin the description of the present invention. Therefore, a detailed ofthe process of demultiplexing the enhanced data will be omitted forsimplicity.

The first descrambler 504 receives the demultiplexed signals from thedemultiplexer 503 and then descrambles the received signals. At thispoint, the first descrambler 504 may receive the authentication resultreceived from the authentication unit 508 and other data required forthe descrambling process, so as to perform the descrambling process. Theaudio decoder 505 and the video decoder 506 receive the signalsdescrambled by the first descrambler 504, which are then decoded andoutputted. Alternatively, if the first descrambler 504 did not performthe descrambling process, then the audio decoder 505 and the videodecoder 506 directly decode and output the received signals. In thiscase, the decoded signals are received and then descrambled by thesecond descrambler 507 and processed accordingly.

As described above, the DTV receiver and method of processing dataaccording to the present invention has the following advantages. Morespecifically, the DTV receiver and method of processing data accordingto the present invention is highly protected against (or resistant to)any error that may occur when transmitting supplemental data through achannel. And, the present invention is also highly compatible to theconventional VSB receiving system. Moreover, the present invention mayalso receive the supplemental data without any error even in channelshaving severe ghost effect and noise.

Additionally, by inserting known data in a specific place (or position)of the data domain and transmitting the processed data, the receivingperformance of the digital broadcast (or digital television) receiverliable to a frequent change in channel may be enhanced. The presentinvention is even more effective when applied to mobile and portablereceivers, which are also liable to a frequent change in channel andwhich require robustness against intense noise. Finally, by performing asoft decision on the enhanced data and outputting the processed datafrom the SISO decoder of the receiving system, the present invention mayenhanced the performance of the additional error correction decodingprocess.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A digital television (DTV) transmitter comprising: a first encoderfor convolutional encoding enhanced data at a coding rate of 1/N,wherein N is greater than 1; a deinterleaver for deinterleaving theconvolutional encoded enhanced data; a second encoder for Reed Solomon(RS) encoding the deinterleaved enhanced data by adding first paritydata to the deinterleaved enhanced data; an interleaver for interleavingthe RS-encoded enhanced data; a third encoder for trellis encoding theinterleaved enhanced data and known data sequences, wherein at least onememory in the third encoder is initialized by initialization data at astart of each known data sequence; a compatible processor forcalculating second parity data based on the initialization data,replacing corresponding first parity data with the second parity dataand outputting the replaced second parity data to the third encoder; amultiplexer for multiplexing the trellis encoded data with segmentsynchronization data and field synchronization data; and a modulator formodulating a broadcast signal including the multiplexed data.
 2. The DTVtransmitter of claim 1, further comprising: a converter for convertingsymbols of the convolutional encoded enhanced data into bytes of theconvolutional encoded enhanced data.
 3. The DTV transmitter of claim 1,wherein the initialization data is determined based on a value of the atleast one memory.
 4. The DTV transmitter of claim 1, wherein thebroadcast signal further includes main data, wherein a convolutionalencoding process is not performed on the main data.
 5. A method ofprocessing broadcast data in a digital television (DTV) transmitter, themethod comprising: convolutional encoding, by a first encoder, enhanceddata at a coding rate of 1/N, wherein N is greater than 1;deinterleaving, by a deinterleaver, the convolutional encoded enhanceddata; Reed Solomon (RS) encoding, by a second encoder, the deinterleavedenhanced data by adding first parity data to the deinterleaved enhanceddata; interleaving, by an interleaver, the RS-encoded enhanced data;trellis encoding, by a third encoder, the interleaved enhanced data andknown data sequences, wherein at least one memory in the third encoderis initialized by initialization data at a start of each known datasequence; calculating second parity data based on the initializationdata, replacing corresponding first parity data with the second paritydata and outputting the replaced second parity data to the thirdencoder; multiplexing the trellis encoded data with segmentsynchronization data and field synchronization data; and modulating abroadcast signal including the multiplexed data.
 6. The method of claim5, further comprising: converting symbols of the convolutional encodedenhanced data into bytes of the convolutional encoded enhanced data. 7.The method of claim 5, wherein the initialization data is determinedbased on a value of the at least one memory.
 8. The method of claim 5,wherein the broadcast signal further includes main data, wherein aconvolutional encoding process is not performed on the main data.